Priya Basil with her sister

'You can marry any man you want – as long as he's Sikh." This warning was issued to me and my sister, by our parents, at an early age. Most children accept such nonsense without question. I'm ashamed to say I did, too, even though I was struck by the dissonance between the parental caution and the fact that nothing about us was especially Sikh. From our short hair, to our penchant for beefburgers, to our inability to name the Ten Gurus of Sikh history, we probably would have been found unacceptable by any truly Sikh family. Nevertheless, I didn't expect I would ever have cause to go against my parents' wishes because, in those days, I didn't like boys.

But then puberty arrived, and I developed a crush on a Muslim guy in our circle of friends. The heart, I started to realise, does not follow orders.

Nothing came of that first infatuation, so it didn't matter that it was theoretically forbidden. But my subsequent romantic leanings didn't conform to expectations either. For people who, by most standards, would be considered decent, liberal and secular, my parents were surprisingly narrow-minded about the kind of men their daughters should consort with. Had I ever settled on a staunch, turbaned and bearded Sikh, I'm sure they would have blackballed him as well. I began to realise that what they had really meant all along was "You can marry anyone – as long as they're exactly like us."

But who were we? There was plenty to distinguish the four members of our immediate family from each other, let alone everybody else. My parents were born in pre-independence Kenya, when social segregation still prevailed. They grew up in a small community predisposed to look out for its own kind. Political events saw them transplanted to Great Britain as teenagers, and no doubt the experience of living there diluted their sense of being Sikh. Consequently, my sister and I never had more than a nominal attachment to the faith. Being looked after by ayahs (nursemaids) from birth meant that our relationship to Africans was different, too. My sister spoke Kiswahili before English or Punjabi. While my parents were disposed to keep a distance from the locals, I was so enamoured of my ayah that I wanted to be black.

My father came home from work one day to find my sister and me, naked and covered in mud, happily playing in the garden with the ayah's children. Outraged, he marched us along the drive to the main road, where, in full view of people walking and driving by, he hosed us down, shouting: "Don't you ever forget who you are!" With the cold jet of water stinging my skin, and the sharp heat of shame crawling underneath it, I didn't think I would.

In reality, it was hard to remember exactly who we were as the school we attended was a bastion of Britishness and Christianity, our closest friends were Muslim and most of the people around us were black. Mostly, my sister and I mediated these disparate facets of our world easily and unselfconsciously. The moments of disconnection, of alienation, came when we tried to follow our parents – who, ironically, wanted only to protect us.

What are we trying to safeguard when we refuse to admit into our circle someone we perceive as "other"? Everyone treasures their customs, traditions and language, but you might think, from the resistance shown by many to mixed-marriages, that faith or culture are fragile constructs, ready to disintegrate if even one more outsider is admitted. But nothing of value is preserved when ideology acts like aspic, trapping people in the jelly of dogma.

My parents were divorced and the family had moved to London by the time, aged 21, I met the man I knew I wanted to spend the rest of my life with. I mention their altered marriage status, and the new location, in order to emphasise that our family had already deviated from the conventional model of an intact unit, well rooted in a community. All the more reason, you might think, for the children to marry well and restore the family's credentials. Well, yes, if that involves making a wholehearted commitment to a person you believe to be your soulmate. What better tribute is there to family values than a successful marriage? The unfortunate thing is that for many people, especially Indians, a good mate is, first and foremost, one of the same background, and success means sticking together regardless of whether you're happy or not.

It's not as if I was the first in my family to be with someone who was not Indian. My mum's brother was married to a wonderful English woman; my father's brother to a lovely Welsh lady. Even my grandfather has a couple of renegade siblings who have hitched up with non-Indians. But outrage seems to hit afresh whenever the next generation shows signs of not conforming. My mother forbade me to speak my partner's name in her presence. She refused to meet him. I think she hoped that, if she didn't admit him into her reality, he would fade away, and she would never have to deal with the issue.

Disapproval is never easy to handle, but when it's directed at your partner it's especially difficult. This person – your other half – supposedly encapsulates all the qualities you value, and also reflects your own sense of worth. Any rejection of them is indirect rejection of you. Much of the thrill of my new love was eclipsed by unhappiness because relations with my family became so strained. Initially, I didn't fully reveal to my partner the extent of their resistance to him. I suppose I was afraid he'd be offended, or think that my family (and therefore maybe me, too) was seriously deranged.

When, after months of not meeting them, he fully understood the situation, he was remarkably sanguine. "They don't know me," he said, "they'll change their minds eventually."

The problem was that they thought they did know him because they were well aware of certain basic personal facts, which many Indians consider the most crucial: age, religion and family background. In other words, they knew he was 12 years older than me, an atheist and divorced. "What would people say?" They worried, as if these shocking details were just the first hints of a much more sinister biography. In fact, time proved to them that behind the superficial indicators of difference there was a wonderful man, who was like them in certain essential ways – above all, in how he loved and wanted the best for me.

Forbidden love is a common story. If people have not experienced it personally, they'll have read about it, or seen various friends and relatives suffer some version of the dilemma. Often in such situations, things don't work out well for all involved, and I found myself wondering why this was the case. Had I just been lucky? Was the fact that I was not so culturally rooted an advantage? Did other men and women not love each other enough? Were other families more intolerant, and more forceful in their expression of that? Did the fact that my parents were divorced, and the family therefore "broken", mean that they couldn't put as much pressure on me as they might otherwise have done?

Despite my deep love for my family, it was always clear which way I would turn if forced to choose between them and my partner. It's not that straightforward for everyone. I'm intrigued by the awful possibility that even true love might not be enough to help one rise above differences.

Rosa Luxemburg said: "Those who do not move, do not notice their chains." It might be cosy to hunker down in the old comfort zone, but the sense of security is false. Too many of us are trapped by an unwillingness to see things differently, to act outside received social norms. We diminish ourselves when we do not accept one another as we are. Acceptance confirms a confidence in one's own values, acknowledges the right to difference, and shows respect for the other. Love does not need to tear us apart.

The Obscure Logic of the Heart by Priya Basil is published by Random House for £12.99. To order a copy for £9.99 with free UK p&p, go to guardian.co.uk/bookshop or call 0330 333 6846